Wireless devices are becoming more diverse with not just billions of phones but also possibly a much larger number of sensors, machines contributing to machine-to-machine communication, and practical everything in the so called Internet of Things (IoT). With an anticipated growth in several orders of magnitude of the number of these devices by year 2020, dense radio networks may likely emerge. Both data and signaling from mobile devices are expected to grow exponentially over the next five or more years. However, localized data traffic patterns may dominate. A centralized architecture in mobile networks such as the Third Generation Partnership Project (3GPP) network to serve all the wireless nodes with a centralized core network is then not efficient. Meanwhile, the Internet peering model is undergoing a transformation from a hierarchical model to a flatter one where tier 2 and tier 3 Internet Service Providers (ISPs) can connect directly with each other without having to always route packets between them via connections to tier 1 ISP. The evolution from a centralized mobile core network towards a more distributed network is then a clear trend.
5G wireless services will require capabilities to support more diverse applications with a much larger range of delay tolerance and data rates than in the current mobile networks. The METIS project in EU FP-7 is exploring a mobile network for year 2020 with much higher bandwidth and lower latencies using multiple radio access technologies. The current 3GPP Evolved Packet Core (EPC) network (Section II.A) relies on lengthy backhauls to the centralized core. End user Packet Data Network (PDN) connections are transported over either a General Radio Packet Service Tunneling Protocol (GTP) tunnel or a proxy mobile IP (PMIP) tunnel, over which the user's IP data packet is encapsulated. The PDN connections are backhauled over various transport networks including Multiprotocol Label Switching (MPLS) to rather centralized EPC nodes, adding delay and complexity to the provisioning of the entire path. In addition, as the total number of end user connections increase in the future, continued centralization of EPC networks will require the support of even larger sets of connection state in the transport plane. In distributed EPC networks, the backhaul to the radio network will naturally be shorter, and the connection state more manageable.